CHICKEN MACROPHAGE ACTIVATION BY INTERFERON - DO BIRDS LACK THE MOLECULAR HOMOLOG OF MAMMALIAN INTERFERON-GAMMA

In mammalian species, interferon-gamma (IFN-gamma) is a lymphokine with a wide range of biological effects, of which the antiviral and macrophage-activating capacities are those best characterized. In birds, no equivalent with similar range of actions has as yet been isolated. Chicken splenocytes were stimulated by mitogens in conditions that were similar to those used for the induction of mammalian IFN-gamma. Culture fluids were assayed for antiviral and macrophage-activating capacities. As much as 1000 units/ml of an interferon-like antiviral activity was found in the culture fluid of Staphylococcus aureus lysate-induced spleen cells. Seroneutralizations assays with a polyclonal antiserum against purified interferon and physicochemical studies revealed that the antiviral activity is identical to or closely related to type I interferon (interferon-alpha/beta). The presence of macrophage activating factors (MAF) in the splenocyte medium was demonstrated by measuring increased production of H2O2 by chicken peritoneal macrophage cultures and a chicken macrophage cell line (HD11). The heat stability of this MAF activity was similar to that of the antiviral factor, and was completely neutralized by the anti-IFN-alpha/beta antiserum. These results show that when the classical procedure used for the productions of mammalian IFN-gamma is applied to chicken splenocytes, it does not yield an equivalent for IFN-gamma/MAF. This suggests that the classification of interferons into types (alpha, beta and gamma), while generally applicable in mammals, may not be applicable in birds.